Vacuum hot top for ingot mold



Jan. 20, 1959 E. P. BYTHROW 2,869,192

VACUUM HOT TOP FOR meow MOLD Fileq Au 8, 1957 2 Sheets-Sheet 1 .l l .1 i I I i I I IO l l a l i l PIC-3.2 4 l i i l I l I INVENTOR. i ELLSWORTH P, BYTHROW I 1 30a; BY a; 1 1

ATTORNEYS Jan. 20, 1959 E. P. BYTHROW 2,869,192

VACUUM HOT TOP FOR INGOT MOLD Filed Aug. 8, 1957 2 Sheets-Sheet 2 INVENTOR. ELLSWORTH P. BYTHROW BY az 7 7 7% W PIC-3.6

M m I ATTORNEYS United States This inventionrelates to improvements in a vacuum hot {tip for an ingot mold used in the casting of steel and the One of the objects of the present invention isto provide a fully enclosed hot top or sinkhead which is adapted to be placed directly into the molten metal at the top of an ingot mold, after which the bottom of the hot top is placed in communication with the molten metal, thereby permitting a previously created vacuum in the hot top chamber to suck up the metal in the mold, thereby scavenging particles of refractory, dirt, heavily segregated metal and gases into the hot top, thereby improving the ingot below the hot top.

Another object of the present invention is to provide a hot top as defined in the preceding paragraph having a fusible seal in the lower end thereof adapted to be submerged in molten metal and fused thereby automatically creating liquid communication between the molten metal .and the interior chamber of the hot-top.

'while the metal is teemed into the mold, and thereafter moving the heavy hot top into proper position over the mold, then down into the metal in the mold, and then releasing the same. 7

Other objects and advantages of my invention will be appear in the accompanying drawings and description and the essential features will be set forth in the apppended claims.

In the drawings- Fig. 1 is fragmental side elevational view of an upper portion of an ingot mold equipped with my invention and showing a fragmentary view of the hot top held in ready position while .the molten metal is teemed into the mold;

Fig. 2 is a side elevational view of the mold after the metal has been teemed into the same and with my improved hot top approaching the position where it is lowered into the mold;

Fig. 3 is a view similar to the upper portion of Fig. 2

with my hop top in its final position in the mold after its bottom seal has been broken and some of the molten metal has moved up into the hot top, some of the parts being broken away to more clearly disclose the action taking place;

Fig. 4 is a fragmentalperspective view of the upper portion of an ingot mold with my hot top handling mechanism in position but without any hot top actually being .shown, in the drawing;

Fig. 5 is a top plan view of my improved hot top con- J atent O 2,869,192 Patented Jan. 20, 1959 metal next to the mold and to the stool is chilled by contact with the cold surfaces and solidifies on the bottom and sides to form what is called the skin of the ingot. This skin or shell gradually grows in thickness, the growth progressing toward the center until all of the metal is in the solid state. One of the effects of this freezing action is the production of a more or less cone-shaped cavity at the top of the ingot, known as the pipe. Pipes are the result of the contraction of the metal on solidifying in the manner just described. One manner of reducing this pipe is to provide a hot top on top of the regular mold, made of refractory material, so as to hold a small reservoir of molten steel above the regular ingot mold which will gradually feed down into the pipe so as to create a substantially solid ingot near the top of the standard ingot mold. This hot top portion of the ingot is later cut off and thrown away. One of the ditficulties of this type or hot top is that it must be placed in position before the metal is teemed into the mold and, sinceit is of smaller cross section than the usual top of the mold, it is more'ditficult to teem the metal rapidly into the mold. My invention does away with this difficulty.

During the cooling of the metal during casting, occluded gases in the metal rise to the top and another object of my invention is to draw these gases to a point where they will not cause objectionable pockets in the ingot.

Another phenomenon found as steel solidifies in an ingot mold is known as segregation. Some of the ingredients in the steel freeze at a lower temperature than the iron. Thus, a process of selective freezing goes on as the steel cools down. Under such conditions, it is to be expected that the substances with the low melting points would be found in one spot or locality in the ingot and that this spot would be located near the top and center of the ingot. It is another purpose of my invention to draw more highly segregated portions of the metal up into the hot top where it may be thrown away leaving the rest of the ingot of a more homogeneous analysis.

Another cause of difliculty in steel are non-metallic inclusions which usually involve particles of slag which come over from the furnace bath, small particles of refractory broken off from the furnace, runners, or ladle, and other bits of dirt'from one source or another. These particles tend to float at the top of the molten steel, and it is another object of my invention to pull these particles, or as many of them as possible, up into the hot top where they may be thrown away later.

I am aware that vacuum has been used in an attempt to draw the molten metal in the upper central portion of the ingot into a position where it may be segregated and thrown away. However, these attempts have not been successful and therefore one of the objects of my invention is to provide a source of rather high vacuum immediately adjacent the molten steel and placed in communication with the molten steel at a critical instant so as to achieve the desired results.

In Figs. 1 to 4 of the drawings, I have shown an ingot mold 10, open at the top, and having side walls and a bottom which is either completely closed or, is in any case closed by resting upon a stool (not shown). In some cases a small opening 10a is provided in the bottom of the ingot mold so that metal solidifies in this opening and assists in stripping the ingot from the mold after it has solidified. I have shown an ingot mold where the large end of the ingot is up, but those skilled in this art will understand that my invention will work with the large end down, as is sometimes the case.

While my improved hot top may be applied to the molten metal in the ingot mold in any desired manner, I have shown a preferred embodiment wherein a handling frame 11 is oscillatably secured to the side walls near the top of the mold by means of two oppositely aligned bolts 12 which provide a horizontal pivot about which the frame 11 may be oscillated approximately 90 degrees in carrying out my invention. The frame 11 has two opposed parallel end pieces 13, each of which has a suitable counterweight 14 attached to its lower end below the bolts 12. At its upper end, the frame bends laterally toward the left in the various views to provide a connecting U-shape portion 15. Toward the right in the various views, the frame has two generally horizontally extending track supports 16, the upper surfaces of which provide a pair of parallel-tracks 16a sloping slightly downwardly toward thecenter of the ingot mold. The track supports 16 are connected at their outer ends by a cross member 17. Notches 18 are provided at each side of the frame between the members 16 and 17 to hold the hot top in the ready position. Parallel elongated vertical recesses 19 are provided on each side of the frame between the members and 16, these notches extending downwardly to a positionslightly above the top of the mold 10 and in that position where the upper portion of my improved hot top is to be held when it reaches its final position as shown in Fig. 3.

A pair of hooks are provided for handling the frame 11. Each hook 20 has a handle portion 20a which is adjacent and parallel to the end members 13 and pivotally attached thereto on horizontally aligned pivots 21. At the lower end of each hook member is the hook proper 20b which extends away from the portion 20a toward the members 16 and 17. The hooks are connected at their upper ends by a bail 22. A stud 16b is rigidly secured in each of the members 16 in position to be engaged by its associated hook 20b.

My improved hot top may take several forms but a preferred form is shown in Figs. 5 and 6. The base member 23 by which the hot top is supported and manipulated comprises a generally rectangular plate or casting having opposed generally horizontally extending trunnions 24. The hot top itself comprises a shell 25 of steel plate or the like having side walls and a top, to which is rigidly secured a stem 25a which extends upwardly through a suitable opening 23a in the base. A metal wedge 26 is driven through a suitable slot in the stem 25a to hold the parts assembled as shown in Figs. 5 and 6. The shell 25 is lined with a suitable refractory such as fire clay as indicated in Figs. 3 and 6. This lining is indicated at 27. A sleeve 28 is secured to the shell 25 and extends through the clay to the inner face thereof as clearly shown in Fig. 6. This sleeve has an inner shoulder 29 forming a valve seat against which a ball 30 seats to provide a valve. These are finely ground parts so as to hold a high vacuum. A pin 31 fastened in the sleeve 28 crosswise of the through passageway prevents escape of the ball 30. A plug 32 is preferably threaded into the outer end of the sleeve 28 to close the same.

Means is provided for closing the lower end of the chamber 33 in the hot top and provided with a fusible closure adapted to be melted by the molten steel so as to provide communication between the molten steel and the chamber 33 when the two come together. This fusible member need not extend over the entire area of the bottom of chamber 33, but in Fig. 6 I have shown such a construction. Here an aluminum plate 34 is adapted to enclose the entire lower end of the hot top. The plate is preferably chiefly aluminum,'or aluminum coated with ferric oxide to provide an exothermic reaction with molten steel to compensate for the chilling effect of immersing the hot top into the molten metal. Preferably, a seal of a heavy plastic rubber cement or the like is provided around the bottom of the hot top and the aluminum plate 34 is then adhered to this rubber cementwhich will set up sufficiently to render the chamber 33 vacuum tight so long as the parts are in the position of Fig. 6.

In the use of my invention, a plurality of hot tops shown in Figs. 5 and 6 are provided and these are previously prepared by having a vacuum line connected after re- 2 and 3, the hot top began to seal itself in the molten moval of plug 32 to the sleeve 28. A vacuum pump is connected to such a line to pull a very high vacuum in the chamber 33. The steel shell 25 and the aluminum plate 34 provide an air tight compartment for this purpose. The ball 30 is sucked away from its seat by the vacuum and will be pulled down against the seat 29 as soon as the vacuum connection is broken. Then, the plug 32 is placed in position to insure that the valve 30 does not leak.

With the ingot mold 10 resting upon a stool (not shown), the frame 11 is swung to the' position shown in Fig. 1 and previously prepared hot top is positioned as shown in Fig. 1 with its trunnions 24 resting in the notches 18. This is the position of the parts while the metal is teemed into the open top of the mold 10. Immediately after the metal is poured, say to the level of a line such as A in Fig. 2 near the top of the mold, the frame 11 is swung, as by engaging the bail 22 and swinging it in a counterclockwise direction about the pivots 21, as indicated by the arrow in Fig. 1, so as to turn the frame 11 through approximately degrees to the position shown in Fig. 2. Stop pins 37 are provided on opposite sides of the mold and rigid therewith to prevent further movement of members 13 past the position shown in Fig. 4. The trunnions 24 of the hot top will then slide slowly down the inclined tracks 16a toward a position above the mold 10. To facilitate this action, the inclination of the tracks 16a is properly chosen and these tracks may be greased ahead of time if desired. As the trunnions 24 continue toward the left from the full line position shown in Fig. 2, they arrive over the slots or recesses 19 and then start to pass downwardly in these recesses as indicated by the broken line position of the trunnions shown in Fig. 2. The handles 20a provide means for easing the trunnions 24 between the broken and full line positions of Fig. 2. The trunnions will then fall down as far as the hooks 20b which will temporarily halt the downward movement of the hot top. The hooks may then be swung above their pivots 21 to the position shown in Fig. 3 allowing the trunnions 24 to drop to the bottom of the slots or recesses 19 to the final resting position of the hot top as indicated in Fig. 3. Very promptly after reaching this position, the aluminum plate 34 will be melted at the temperature of the molten steel 36 at the same time giving an exothermic (Goldschmidt) reaction thereby raising the temperature of the molten metal in the hot top. This will provide communication between chamber 33 and the molten steel which will then rise into the vacuum filled chamber as indicated in Fig. 3, thus lowering the level of the steel around the outside of the shell 25. This will draw the particles of slag, refractory, dirt, heavily segregated metal and gases into the hot top chamber 33.

It should be understood by those familiar with this art that the shell 25 of the hot top may be made of a steel to resist the high temperature of the molten metal or it may be made of cast iron it long life is desired. However, it may be made of cheaper material and, therefore, subject to a shorter life.

It will have been noted that as soon as the lower end of a hot top passed below the molten metal line A of Figs.

steel. After plate 34 melts, this seal persists, the lower ends of the walls of the hot top providing sealing skirts immersed in the hot steel. This seal continues until the metal moves down to a final position such as the level B indicated in Fig. 3. As the metal in the hot top cools, a skin will form around its outer surface and the shrinkage of this skin away from the lining of the hot top will allow air to enter the hot top, thereby permitting remaining molten metal in the center of the hot top to descend and fill the cavities which tend to form in the upper central portion of the ingot.

My invention thus provides a cheap and simple manner of applying a high vacuum to the upper central portion of the molten metal at the top of an ingot so as to draw undesirable portions of the molten steel up into the hot top, but the hot top is not placed in position until after the metal is teemed into the mold, thus allowing the use of a larger nozzle while teeming, and, therefore, saving the time of pouring a heat into the ingot mold. The hot top is easily stripped from the top of the ingot after it has solidified, permitting the stripping of the ingot from the mold 10.

What is claimed is:

l. A hot top for use at the upper end of a mold filled with molten metal and comprising a closed chamber having at least its inner surface formed of refractory material and capable of holding a vacuum, the bottom of said chamber including a passageway and means closing said passageway fusible at the temperature of the molten metal in said mold.

2. A hot top as in claim 1 including means for holding the same with the bottom of said chamber sealed in the molten metal in said mold.

3. The method of applying vacuum to the upper central portion of molten metal in an open-top mold comprising partially submerging in said metal a closed container having a vacuum therein, and thereafter establish.- ing communication between the interior of said container and said molten metal.

4. A hot top for use at the upper end of a mold filled with molten metal and comprising a closed chamber having at least its inner surface formed of refractory material and capable of holding a vacuum, the bottom of said chamber being closed by a plate fusible at the temperature of the molten metal in said mold.

5. A hot top for use at the upper end of a mold filled with molten steel and comprising a closed chamber having at least its inner surface formed of refractory material and capable of holding a vacuum, the bottom of said chamber being closed by a plate chosen from the group consisting of chiefly aluminum and aluminum plus ferric oxide.

6. In combination, a metal mold having an open top, a frame mounted on said mold and having a track leading from a position clear of said mold to a position over said 6 mold, a hot top comprising a closed container having a readily openable passage near the bottom thereof, said hot top having means supporting it on said track for movement therealong to a position over said mold and said frame providing means for loweringsaid hot top to a position where said passage is inside of said mold.

7. The combination of claim 6, wherein said frame is mounted on said mold for oscillation about a horizontal axis into two positions, in one of which positions gravity acting on said hot top holds it on said track clear of said mold, and in the other of said positions gravity urges said hot top along said track toward said mold.

8. The combination of claim 7 wherein said last named means includes recess means in said frame communicating with the mold end of said track and coacting with said hot top to direct at least the lower portion thereof into said mold.

9. The combination of claim 8 wherein said frame provides parallel tracks on opposite sides of said mold, said means supporting said hot top on said track are trunnions resting on said tracks, said recess means comprises two recesses in said frame extending one from each of said tracks downwardly toward said mold when said frame holds said hot top over said mold, and two hooks having manipulating arms respectively pivotally connected to said frame on opposite sides of said mold on horizontal axes, each hook arm having its pivot on one side of one of said recesses with the hook on the opposite side of the recess adapted to engage the frame there, said manip ulating arm extending across said recess in position to engage one of said trunnions, whereby said hooks may be operated to oscillate said frame until said trunnion: enter said recesses, and thereafter said manipulating arms can be swung about their pivots to gradually lower said trunnions down said recesses.

References Cited in the file of this patent FOREIGN PATENTS 5,084 Great Britain Jan. 18, 1825 

